There are known vertical packaging machines that comprise a feeder that supplies a laminar film, a forming tool adapted to give a tubular shape to the laminar film, forming a laminar tube, and at least two advance modules, each one of which comprises at least one drive belt arranged facing the forming tool. The drive belts, as they move, cause the movement of the laminar tube towards one end of the exit of the forming tool. In addition, these machines comprise longitudinal sealing means adapted to seal longitudinally the two longitudinal ends of the laminar film that forms the laminar tube, and transverse cutting and sealing means to generate packaging from the laminar tube, once the products to be packaged have been inserted into the interior of the forming tool. Vertical packaging machines of these characteristics are described in GB2096091A, US4800707 and EP0832818A1.
GB2096091 also discloses a specific type of vertical packaging machine, of the type that causes the movement of the laminar tube by vacuum in relation to the advance means. In the vertical vacuum packaging machine the suction of the laminar tube is caused by the drive belts, towards them, generating a connection by means of friction between the belts and the laminar tube. Said connection by friction forces the laminar tube to move in conjunction with the movement of the drive belts.
Different sizes of packages may be obtained by exchanging the forming tool. For the purpose of detecting that the operator positions the forming tool with the correct dimensions in order to obtain the required packaging, EP832818A1 describes a vertical packaging machine that comprises conveyor belt-type movement means that move the advance means from reference positions towards the laminar tube, and means for measuring the distance travelled by the movement means, which allow the dimensions of the forming tool to be identified and ensure that the operator has placed the tool corresponding to the package to be obtained.
Finally, U.S. Pat. No. 4,800,707 describes a vertical packaging machine that comprises servomotors that move the advance means in a horizontal direction, moving them towards or away from the forming tool to adjust the vertical packaging machine according to the size of the forming tool during the setting up of the machine.